Intro to ORMs

orm.rb

require 'pg'

CONN = PG::Connection.new({
    host: 'localhost',
    user: 'murat',
    password: '',
    dbname: 'lighthouse_2015_10'
})



# ORM: object relational model
class ORM

    def initialize(object_hash)
        object_hash.each do |column, value|
            instance_variable_set("@#{column}", value)
            self.class.send(:attr_accessor, column.to_sym)
        end
    end

    def instance_variables_hash
        Hash[instance_variables.map { |name| [name[1..-1], instance_variable_get(name)] } ]
    end

    def to_s
        instance_variables_hash.inspect
    end

    def self.convert_to_objects(results)
        objects = []
        results.each do |result|
            object = self.new(result)
            objects << object
        end

        return objects
    end

    def get_table_name
        return "#{self.class.name.downcase}s"
    end
    def self.get_table_name
        return "#{self.name.downcase}s"
    end

    def self.all
        results = CONN.exec_params("SELECT * FROM #{get_table_name}")
        return convert_to_objects(results)
    end

    def self.search(column, name)
        results = CONN.exec_params("SELECT * FROM #{get_table_name} WHERE #{column} ILIKE '%#{name}%'")
        return convert_to_objects(results)
    end

    def self.find_by_id(id)
        results = CONN.exec_params("SELECT * FROM #{get_table_name} WHERE id=#{id}")
        objects = convert_to_objects(results)

        if objects.length > 1
            raise Exception, "Find by ID returned too many results"
        else
            return objects[0]
        end
    end

    def save

        if @id
            # update
            columns = instance_variables_hash.keys.join(", ")
            values = instance_variables_hash.values.map { |v|  "'#{v}'" }.join(", ")

            statements = instance_variables_hash.select do |key, val|
                key != "id"
            end.map do |key, val|
                "#{key}='#{val}'"
            end

            puts "UPDATING"
            query = "UPDATE #{get_table_name} SET #{statements.join(', ')} WHERE id=#{@id}"
            puts query
        else
            columns = instance_variables_hash.keys.join(", ")
            values = instance_variables_hash.values.map { |v|  "'#{v}'" }.join(", ")

            puts "INSERTING"
            query = "INSERT INTO #{get_table_name} (#{columns}) VALUES (#{values})"
            puts query
        end
        CONN.exec_params(query)
    end

end

class Book < ORM
end

class Better_table < ORM
end

existing_table = Better_table.find_by_id(1)
puts existing_table
existing_table.color = "orange"
existing_table.save

existing_table = Better_table.find_by_id(1)
puts existing_table

orm_basics.rb

require 'pg'

CONN = PG::Connection.new({
    host: 'localhost',
    user: 'murat',
    password: '',
    dbname: 'lighthouse_2015_10'
})



class Book

    def initialize(book_hash)
        book_hash.each do |column, value|
            instance_variable_set("@#{column}", value)
        end
    end
    def to_s
        return "#{@title}, by #{@author_id}"
    end

    def self.convert_to_objects(results)
        books = []
        results.each do |result|
            book = Book.new(result)
            books << book
        end

        return books
    end

    def self.all
        results = CONN.exec_params("SELECT * FROM books")
        return convert_to_objects(results)
    end

    def search(name)
        results = CONN.exec_params("SELECT * FROM books WHERE title ILIKE '%#{name}%'")
        return convert_to_objects(results)
    end
end

#Book.all.each do |book|
#    puts book
#end
#puts "-----"

class Author

    def initialize(author_hash)
        author_hash.each do |column, value|
            instance_variable_set("@#{column}", value)
        end
    end
    def to_s
        return "#{@first_name} #{@last_name}"
    end

    def self.convert_to_objects(results)
        authors = []
        results.each do |result|
            author = Author.new(result)
            authors << author
        end

        return authors
    end

    def self.all
        results = CONN.exec_params("SELECT * FROM authors")
        return convert_to_objects(results)
    end

    def search(name)
        results = CONN.exec_params("SELECT * FROM authors WHERE first_name ILIKE '%#{name}%' OR last_name ILIKE '%#{name}%'")
        return convert_to_objects(results)
    end
    
end